This invention relates to low-resistance electrode constructions of electrically conducting non-metal (ceramic, semiconductor, or carbon-based) electrodes that have metal current leads as terminals. This invention also relates to the electrochemical cells using the low-resistance electrodes in electrochemical technologies, particularly for producing metal such as Li, V, U, lanthanides, Al, and the like from the corresponding soluble metal oxide, or halide salt, which is known as electrowinning. The low-resistance electrode construction includes a stable, electrically conductive ceramic or graphite with a hollow interior filled at least in part with a metal which is liquid at the cell""s operating temperature. The liquid metal provides reduced resistance connection between the electrode body and the metal current lead acting as a terminal contact resistance between the non-metal electrode body and metal current lead are reduced by the use of liquid metal. Moreover, adverse effects from the thermal cycling of the metal compression fittings between the metal current lead or terminal and the non metallic electrode are obviated, thus reducing the propensity of the electrodes to crack due to the differences in coefficients of expansion between the ceramic and metal. While the preferred electrodes hereafter disclosed used ceramics of SnO2 doped with antimony and copper for lowered electrical resistance, and with tin as the liquid metal, it is believed that the invention applies broadly to other stable, electrically conductive ceramics such as TiB2. In addition to tin, other metals may be used in the hollow interior to lower resistance between the ceramic and power source or mercury such as gallium or mercury for low-temperature applications and also Bi, Cd, Na and Li, as well as alloys thereof for higher temperature applications.
Broadly, the inventive low-resistance electrode for an electrochemical cell may be described as an electrically conductive ceramic or carbon shape with a hollow interior filled at least in part with a metal that is liquid at the cell""s operating temperature. A critical feature of the inventive anode construction is the current pathway through a solid metal, a liquid metal, and non-metal electrical conductor. The ceramic receptacle may also be doped to improve its electrical conductivity.
Accordingly, it is an object of the invention to provide an electrode comprising, a non-metal electrically conducting receptacle defining a chamber, a first metal having a melting point in the range of from about room temperature to about 800xc2x0 C. inside the receptacle chamber, and a second metal that is solid at the operating temperature of the electrochemical cell in contact with the first metal inside the receptacle chamber and extending outside of the receptacle chamber forming a terminal for the electrode.
Another object of the invention is to provide an electrochemical cell comprising a cathode and an anode in contact with an electrolyte, the anode having an electrically conducting non-metal receptacle defining a chamber, a first metal having a melting point in the range of from about room temperature to about 800xc2x0 C. inside the receptacle chamber, and a second metal that is solid at the operating temperature of the electrochemical cell in contact with the first metal inside the receptacle chamber and extending outside of the receptacle chamber forming a terminal for the anode, the electrolyte including the oxides, halides or mixtures thereof of one or more of Li, V, U, Al and the lanthanides.
Yet another object of the invention is to provide a method of producing a metal or an alloy from the oxides or halides or mixtures of the oxides and halides of the metal or the alloy constituents, comprising operating an electrochemical cell having a cathode with a terminal and an anode with a terminal in contact with an electrolyte, the anode having an electrically conducting non-metal receptacle defining a chamber, a first metal having a melting point in the range of from about room temperature to about 800xc2x0 C. inside the receptacle chamber, a second metal that is solid at the operating temperature of the electrochemical cell in contact with the first metal inside the receptacle chamber and extending outside of said receptacle chamber forming a terminal for the anode, the electrolyte including the oxides, halides or mixtures thereof of one or more of Li, V, U, Al and the lanthanides, and establishing a potential across the cathode terminal and anode terminal to cause metal oxides or halides of Li, V, U, Al and the lanthanides in the electrolyte to be reduced to the metal or an alloy at the cathode and for oxygen or other gas as appropriate to be evolved at the anode.
The invention consists of certain novel features and a combination of parts hereinafter fully described, illustrated in the accompanying drawings, and particularly pointed out in the appended claims, it being understood that various changes in the details may be made without departing from the spirit, or sacrificing any of the advantages of the present invention.